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BaBar Radiative Penguin Physics at SCIPP

DOE SITE VISIT Monday, July 27, 2011. BaBar. BaBar Radiative Penguin Physics at SCIPP. Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz. People. Senior Al Eisner (volunteer) Bruce Schumm Student

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BaBar Radiative Penguin Physics at SCIPP

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  1. DOE SITE VISIT Monday, July 27, 2011 BaBar BaBar Radiative Penguin Physics at SCIPP Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz

  2. People • Senior • Al Eisner (volunteer) • Bruce Schumm • Student • Joel Martinez (B   Ph.D. expected 9/2011) • Post-doc • William Panduro-Vazquez (volunteer; now an ATLAS postdoc at) 2010 DOE Site Visit

  3. Outline • Effective Neutral Currents: General Motivation • b  s Penguins • SUSY parameter space implications • b  s “Inclusive” approach • b  d Penguins and |Vtd/Vts| • Motivation • B→Xd “Semi-Inclusive” approach • Status of |Vtd/Vts| • CP Violation in B →ρog • Conclusions 2010 DOE Site Visit

  4. Effective Neutral Currents and Radiative Penguins The SM b  s(d)  transition is high order (two weak plus one EM vertex) … Vtb Vt(s,d) so new physics can enter at leading order: + photon off any charged leg (d) (d) (d) Although rare (~ 5x10-4 for s and ~10-5 for d), the isolated high-energy photon is a powerful signature. 2010 DOE Site Visit

  5. Outline • Effective Neutral Currents: General Motivation • b  s • SUSY parameter space implications • Inclusive approach • b  d and |Vtd/Vts| • Motivation • B→Xd (“Semi-Inclusive” Approach) • Status of |Vtd/Vts| • CP Violation in B00 • Conclusions 2010 DOE Site Visit

  6. B  s and SUSY Parameter Space C.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo, “Supersymmetry Without Prejudice”, arXiv:0812.0980v1 [hep-ph] Explore 107 points over 19-dimensional parameter space of CP-conserving MSSM b  s most effective constraint (72% of models surviving prior constraints are eliminated; better than direct searches for SUSY partners) 2010 DOE Site Visit

  7. B Factory Data Sets 440 fb-1 700 fb-1 2010 DOE Site Visit

  8. qq + ττ BB XSγ Inclusive Measurement of b  s: Introduction Most exacting approach (“Inclusive”) is aggressive: Use only high-energy  as signature Suppress continuum with event shapes, requirement of a high-energy lepton. Estimate remaining continuum by scaling off-peak data. Challenge: background from 0()   decays (plus some fakes) in B decays 2010 DOE Site Visit

  9. Inclusive Measurement of b  s: Signal/Background Sig. Region B/Bbar background control region BB Cont. Signal • Most prominent SCIPP Contributions: • 0,  rejection and backgrounds • Anti-neutron backgrounds • BAD editor (Eisner) 2010 DOE Site Visit

  10. Inclusive Semi-Inclusive Inclusive Inclusive Inclusive Summary of Measurements of the b  s Rate Collaborating with SLAC, Notre Dame; SCIPP playing central role since 2003 (Schmitz thesis, Winstrom candidacy project) A. Limosani, Melbourne BaBar Result on 360 fb-1 is finalized: 2010 DOE Site Visit

  11. Expected Errors (all major uncertainties included) Branching Fraction Results (x 104) Quoted errors: (stat%)  (syst%) BABAR Runs I-V E* > 2.02.80  0.12  0.14   6.6% E* > 1.93.00 0.14  0.19   7.9% E* > 1.83.20 0.15  0.29   10.2% BELLE 605 fb-1 E* > 1.8 3.24  0.17  0.24   9.1 % Expect to quote preliminary result for E* > 1.8 this summer (ICHEP) 2010 DOE Site Visit

  12. Unblinded Spectrum (not yet public) Runs I-V NOT YET PUBLIC Signal Photons per 0.1 GeV SIGNAL REGION E* But: Predictions are in B rest frame  unfold detector smearing and boosts… 2010 DOE Site Visit

  13. Unfolded Spectrum (also not yet public) Procedure: An iterative, dynamically-stabilized method of data unfolding, B. Malaescu, ArXiv 0907:3791 Signal Photons per 0.1 GeV Ecms • Largest effect is boost at kinematic edge. • Nearing review-board approval (!!) • Phys. Rev. D article in prepartation 2010 DOE Site Visit

  14. Outline • Effective Neutral Currents: General Motivation • b  s • SUSY parameter space implications • Inclusive approach • b  d and |Vtd/Vts| • Motivation • B→Xd (“Semi-Inclusive” Approach) • Status of |Vtd/Vts| • CP Violation in B00 • Conclusions 2010 DOE Site Visit

  15. (d) (d) (d) (d) Vt(s,d) (d) (d) Measuring |Vtd/Vts| Two independent diagrams provide sensitivity to CKM parameter Vtd B Mixing Note: In both cases, hadronic uncertainties minimized by comparing to corresponding Vts process (Bs mixing, b  s)  Observable is | Vtd / Vts | Radiative Penguins 2010 DOE Site Visit

  16. SM effects suppressed by 10-5 relative to mixing |Vtd/Vts| from Penguins: Motivation ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by Di Lodovico (BaBar)]: How do penguins fit into the picture? Mixing: xd = mB/B ~ 1  mB ~ B Penguins: Br(bd) ~ 10-5 d~ 10-5B With |Vtd/Vts| precisely constrained by mixing, b  d is a compelling testbed for new physics. 2010 DOE Site Visit

  17. (and ) Exclusive Approach: B  ()  Standard (“Exclusive”) Approach: measure exclusive rate Br(B  () ); normalize with Br(B  K* ) Annihilation Diagram Values of 2 and R are available from Ali, Parkhomenko, arXiv:hep-ph/0610149 Ball, Zwicky, J. High. Energy Phys. 0604, 046 (2006); Ball, Jones, Zwicky, Phys. Rev. D 75 054004 (2007) 8% uncertainty on extraction of |Vtd/Vts|. 2010 DOE Site Visit

  18. Semi-Inclusive Approach: B  Xd  (Preliminary) Alternative Approach (Runs I-V): Reconstruct seven exclusive final states Xd in range 0.6 GeV/c2 < MXd < 1.8 GeV/c2 ( now published in PRL 102:161803,2009 |Vtd/Vts|2 related to (bd)/(bs) with ~1% theoretical uncertainty [Ali, Asatrian, Greub, Phys. Lett. B 429, 87 (1998)] Collaborating with I.C. London & SLAC New:Include Run VI, re-optimize event selection; extend MXd to 2.0 GeV/c2 2010 DOE Site Visit

  19. # bodies # bodies # 0 # 0 Measured Regions for B  Xd(s)  UNMEASURED XS MEASURED K* Region 1.0 < Mhad < 2.0 2.0 < Mhad 0.6 < Mhad < 1.0 UNMEASURED Xd MEASURED Xd analysis only  and Xd analyses Mhad (MXd) 2010 DOE Site Visit

  20. B  X(s,d)  Decay Width Ratio Results Fit in high-mass Xd region 1.0 < Mhad < 2.0 GeV/c2 BABAR PRELIMINARY E MES First significant observation of b  d above resonant region Primary Exptl Result (prior result: 0.033  0.013  0.009); Submitted to PRL 2010 DOE Site Visit

  21. Expt. Theory Calculation of |Vtd/Vts| BABAR PRELIMINARY Ali Asatrian Greub Submitted to PRL Ratio of partial widths related to |Vtd/Vts| with very small uncertainty 2010 DOE Site Visit

  22. Global Status of |Vtd/Vts| Published Sept 2010: Phys.Rev.D82:051101 No evidence for non-Standard-Model contribution to the b  d decay width. Starting to receive attention from theory community: Crivellin, Mecolli,“B  Xd and Constraints on New Physics” arXiv:1106.5499 2010 DOE Site Visit

  23. Review of Radiative Penguin Transition Rates Invited review: Radiative Penguin transition rates (published in Modern Physics Letters A, August 2010) Invited talk: 2011 Lake Louise Winter Institute 2010 DOE Site Visit

  24. CP Violation in B00 Separate out B0 (“+”) and anti-B0 (“-”) decays; look at asymmetry in time-evolution: Standard Model expectation: C = -0.1 and S = 0 (due to phase cancellation between mixing and t-quark-dominated decay) 2010 DOE Site Visit

  25. 0 expected signal and background • Significant signal-region backgrounds are: • Continuum • Generic B • K- • Small fraction of non-truth-matched signal (no special treatment) 2010 DOE Site Visit

  26. 0 signal kinematic distributions dE MES t 2010 DOE Site Visit

  27. s background kinematic distributions K+- Displaced; broad K0S- Broader tail dE MES t 2010 DOE Site Visit

  28. 0 expected signal and background B+B- B0B0 Significant dE MES t 2010 DOE Site Visit

  29. Continuum kinematic distributions MES dE • Fit components: • Signal • Continuum • Generic B • K+- • K0S- t 2010 DOE Site Visit

  30. Fitting strategy • Plan to employ a two-stage fit: • Fit over full region in dE and MES (ignore t) to establish continuum and normalization and shape and signal normalization • Fit over signal region (including t) to extract S, C, fixing continuum and signal parameters to the values obtained in 1). 2010 DOE Site Visit

  31. 0 CP Violation First-Stage Fit Fit for Nsig: <N> = 50  19 <PULL> = -0.07  0.03 2010 DOE Site Visit

  32. 0 CP Violation Second-Stage Fit Fit for S,C: <S> = 0.47 <PULLS> = 0.01  0.03 2010 DOE Site Visit

  33. Concluding Remarks • SCIPP playing central role in key radiative penguin measurements • Inclusive b  s measurement very challenging; drafting long PRD with 10% (E* > 1.8 GeV) (prior result was 14.5% for E* > 1.9 GeV) • Intensive focus on b  d transition * Rates  Three PRL, one PRD in last three years * CP Violation  Expect result in ~6 months • First observation of non-resonant b  d transition (Impact of b  d signature may not yet be fully appreciated) • Schumm wrote s(d) review article for World Scientific • 5 PhD theses; 6th on the way 2010 DOE Site Visit

  34. Backup Slides 2010 DOE Site Visit

  35. Inclusive Measurement of b  s: B/Bbar Backgrounds Sources of B/Bbar Background (after full selection) 2010 DOE Site Visit

  36. If high-energy  passes selection, then 0,  look for low-energy  and veto event Inclusive Measurement of b  s: 0, Backgrounds Major source of BB background due to high-energy photons from 0()   (67% + 15% = 82% of total BB background according to MC) ~50% of the time the low-energy photon is missing. Modeling of low-energy (30-80 MeV) photon efficiency to ~ 1% critical to lowering systematic error One example of SCIPP group contribution Also: Anti-neutron backgrounds, photon efficiency, … 2010 DOE Site Visit

  37. Inclusive Measurement of b  s: 0, Backgrounds Define cosh  (E,high - E,low)/ (E,high + E,low) = energy asymmetry Signal selection requirement of E* > 1.8 GeV pushes asymmetry up, and energy of 2nd photon down.  Sensitive to reconstruction efficiency for 30-80 MeV photons. Measurement of 0 reconstruction efficiency from ()/() Expected/Measured cosh cosh But: can bootstrap to lower E with dedicated 0 sample 2010 DOE Site Visit

  38. BX(d,s): Correction for Missing Modes • MC Simulation • Two-body Xs(d)  decay; mass spectrum of Xs(d) system given by Kagan-Neubert model • A.L. Kagan, M. Neubert, Phys. Rev. D 58, 094012 (1998) • Fragment Xs system via prior experimental constraint • Fragment Xd system via phase space • Missing modes with 0.6 < MX < 1.0 • MC suggests this region is dominated by resonances ( and ); confirmed by K*dominance of B Xs • Correction for missing modes well understood 2010 DOE Site Visit

  39. BX(d,s): Correction for Missing Modes • Missing Modes with 1.0 < MX < 1.8 • Force 50% of decays to un-weighted mix of higher-mass resonances • Force Xd decay to be identical to Xs decay up to substitution s  d • B  Xd  Resonances • h10 (1170) • b10 (1235) • b1+ (1235) • a10 (1260) • a1+ (1260) • f20 (1270) • f10 (1285) • a20 (1320) • a2+ (1320) • B  XS  Resonances • K1 (1270) • K1 (1400) • K* (1410) • K2*(1430) • K* (1680) 2010 DOE Site Visit

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